A conventional bra generally includes two cups connected by a connection plate and two side plates respectively extend from the two cups so as to be hooked with each other on the back of the wearers. Two shoulder straps are connected between the corresponding pair of cup and side plate. The cups each include a foam lining, a shape wire located at a lower edge of each cup, an inner layer and an outer layer. The foam lining is sandwiched between the inner layer and the outer layer which is sewed to the outer layer. Although the sewing provides better connection to the inner layer and the outer layer, seams are visible if the wearers wear a tight top and the threads could be loosened or broken after repeatedly washing.
The present invention intends to provide a cup structure of a bra and the inner layer and the outer layer are connected with each other by way of heat-pressing which creates a non-seam outer surface for the cups.